Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a first image of a first embodiment of a display screen or portion thereof with transitional graphical user interface according to the claimed design;

FIG. 2 is a front view of a second image of the first embodiment according to the claimed design;

FIG. 3 is a front view of a first image of a second embodiment according to the claimed design; and,

FIG. 4 is a front view of a second image of the second embodiment according to the claimed design.

The longer-length broken-line showing of a device and the shorter-length broken-line showing of a display screen boundary and various elements within the graphical user interface are included for the purpose of illustrating an environment and form no part of the claimed design.

The appearance of the transitional image transitions between the images shown in FIGS. 1-2 and 3-4. The process or period in which one image transitions to another forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 